Bitcoin doesn't need altcoins because it was making its way by its own.Altcoins are dependent on Bitcoin which has been seen over and over again on every rise in price of Bitcoin.Bitcoin will always rule the digital/crytpocurrencies no matter how advanced they will be in tech but still will remain under Bitcoin
I somehow dont agree with you, it is true bitcoin still rule the crypto currency world, but that doesnt mean it can stay like this forever who knows one day it will be replace by other alt coins, despite that a lot of alt coin seems useless but i think its one of the element that keep cryto currencies world interesting, alt coin has help bitcoin a lot because a lot of people doing trading bitcoin with alt coin
I do agree that most altcoins doesn't even have a goal or anything, they are just there and there's ton of them. Without the concept of bitcoin, altcoin wouldn't be there. Altcoin is just a copy of bitcoin. Never have I seen an original idea being replaced by its very own replica (copy). The fact that bitcoin is the original and have been there the longest is enough for us to know that it will be the main cryptocurrency in the following years.
I think the only way that bitcoin will be replaced by an altcoin is when there's an unsolvable problem or a problem that takes a lot of time to get resolved in the bitcoin network. The second best crypto-currency will then take over but the name "crypto-currency" will be damaged as well because of the bitcoin take down.